Boiler tube cleaning blower



C- F. LUMB ET AL BOILER TUBE CLEANING BLOWER Aug. 22, 1950 s Sheets-Sheet 1 Filed March 28, 1944 s- 22, 1950 5. F. LUMB EI'AL 1 2,519,674

BOILER TUBE CLEANING BLowER Filed March 28, 1944 '3 Sheets-Sheet 2 i 45 In 0 ezz/zozis I tomb 1". 611?. 5 6? a e '1)" 49W 6.

'Aug. 22, 1950 c. F. LUMB ETAL v 2,519,674

BOILER TUBE CLEANING BLOWER Filed March '28, 1944 N s Sheets-Sheet 3 Iz?/veJat01 s C, Flu/m5 TGZM as Patented Aug. 22, 1950 umrso STATES {PATENT O Charles Fletcher Lumb, Kingston Hill, and Frank George William Spears, Potters Bar, England Application March 28, 1944, Serial No. 528,430

. In Great Britain January 31, 1944 -Claims.

This invention relates to apparatus forcleaning'boiler tubes and the like, commonly termed soft blowers, of the kind employing a steam ejector which is mounted for reciprocation withinja; steam chest. to assume it operative or inoperative position under the control of an operatingmechanism comprising a screwed spindle cooperating with a nut and which steam ejector is also required to be rotated to cause the steam nozzle, or nozzles, to traverse the required tube area. Although steam is referred to as constitutingthe. cleansing medium it is understood that anyother suitable fluid can be substituted therefOI. i l The invention has for its object to provide a modified and improved and more efiicient construction of such operating mechanism.

, In the accompanying drawings:

. v,E'igure 1 is a longitudinal section of one form of apparatus incorporating the invention,

Figured is a vertical section on the line 2-2, Figure 1' taken in the direction of the arrow with the casing removed, p '1 Figure 2a is a fragmentary top plan view of one end of the piston l5 with parts, removed,

, Figures 3, 4 and 5 are diagrammatic views showing essential parts of the coupling according to the invention shaded in accordance with the Heraldic convention and in their different opera tive positions, t "Figure 6 is a longitudinal section similar to Figure l but of amodified form of the invention,

and. c l

Figure 7 is a detail view showing the piston [5 of Figure 6 as seen from below that figure.

In j'carrying the invention into effect in one convenient manner as illustrated in the drawings, and referring first to Figures l-and 2,'a tube cleaning apparatus or soot blower is provided comprising a steam chest I, in the form of a tubular casing, to the inner end of which there is secured, as by screw-threading 2, a valve seat -3 {of ring formation and beyond which a tubular extension 4 of the steam chest is provided and secured, as by screw-threading 5, to a steam branch 6 in turn jointed at I to the steam chest by means, for example, of studs 8.

The steam ejector 9 is accommodated within the tubular extension 4 of the steam chest and is in theform of a hollow piston having openings 10 at its outer end, throughwhich steam is passed to the piston interior, and a nozzle II at its inner end, through which the steam issues and impinges against the tubes to be cleaned. The ejectorpiston is connected by a tie pin 42, with 2, a block I 3 forming the movable valve part of a simple shut-down valve, the-fixed seat of which is the seat 3 referred to and which movable valve part I3 is in turn connected by another and screwed tie pin I4 with a piston l5 mounted for movement within the steam chest I.

To facilitate the removal of the interior of the apparatus it is only necessary to break the one joint 1 by removal of the nuts 8a from the studs 8. This permits the steam chest and with it the entire interior thereof, including the valve seat, movable shut-down (or alternatively a piston) valve member and the steam ejector, being removed.

In connection with the apparatus as just described, operating mechanism is required to produce the required movements of the steam ejector such that the same may be moved axially to open the valve and then rotated to cause the steam nozzle to traverse the required tube area and the construction of this operating mechanism is preferably such that the first part of the movement of the ejector into the steam projecting or operative position takes place in a straight line or non-rotary manner during which time the valve is fully opened, and is followed by a purely rotary movement of the ejector, at which time the ejector will be receiving a full supply of steam, clue to the fully open position of the valve. On the reverse or retracting movement of the ejector this sequence of movements must take place in the reverse order so that the ejector is first given a purely rotary motion to restore the steam nozzle to its zero position and then the ejector is moved axially to fully close the valve.

The operating mechanism for producing the above sequence of movements of the steam ejector comprises essentially a screwed spindle it and a nut H but the connection of the two is such that the nut may be held stationary and the screwed spindle made tortravel through the nut v (when axial movement of the ejector results) or the nut may be freed to rotate with the screwed spindle (when a rotary movement of the steam ejector results) and the operating mechanism providedby this invention incorporates a mechanical coupling by which this change of the operative conditions between the nut and screwed spindle may take place automatically during the rotation of the screwed spindle and withoutithe need for any consciou effort on the part of the operator, in the case of a hand controlled soot blower installation.

I Referring now to this operating mechanism, at its outer end, remote from the valve 3, I3, the

piston i5 is formed with a slot which is of T- section and is open at the outer end of the leg 22 of the T to receive therein a pair of diametrically opposite fingers 23 which project axially from the inner end of the nut IT so as to lie in the path of the side walls 220. of the leg of the T-slot, and which nut has an internally threaded central bore l'i'a: through which the screwed spindle 16 passes. The latter terminates at its inner end in a flanged disc 28 which is accommodated in the cross slot or top 21 of the T. Thescrewed spindle I8 is centrally disposed within the outer end of the steam chest to extend longitudinally therein and be co-axial with the piston and steam ejector, and at its outer end the screwed spindle is fitted with a radially projecting stud 32 which engages in an axial groove 3:3- in the hub 36 of a hand-wheel 3'! by which the screwed spindle is rotated, and which stud and groove provide a splined connection which permits the screwed spindle to travel axially through the nut when the latter is restrained against rotation'. The central bore or hub of the handwheel is extended forwardly towards the steam chest in the form of a co-axial sleeve 38 which fits within the outer end of the steam chest and has on its outer surface an annular circumferential groove 48 in which the inner ends 410 of set screws or studs 4| engage to prevent endwise or axial movement of the hand-Wheel, the said studs being screwed through holes in the outer end of the steam chest and being conveniently provided with rotatable rings 41b constituting rollers which engage with the outer periphery Ila, of the nut l'l' and serve to take the endwise loads.

With the operating mechanism as thus constructed the screwed spindle I6 is connected with the nozzle through the medium of the disk 28- engaging in the recess 2-? in the piston and the nozzle can have rotary movement imparted thereto or be restrained against rotation without altering' the connection of the screwed spindle with the nozzle. The nut I! is also connected with the nozzle throughthemedium of the fingers Z3 engaging in the slots 22- on the piston such that at the appropriate moment, and when the nut is forced to rotate, the nut may operate to rotate the nozzle without its operative connection with the nozzle being altered.

The operating mechanism provided in accordance with this invention besides providing these connections of the screwed spindle and nut with the nozzle also incorporates, as above mentioned, a mechanical coupling which is operable automatically during the rotation of the screwed spindle to provide positive coupling conditions when the nut is either restrained against rotation with the spindle by being coupled to a fixed part or is freed to rotate therewith by being coupled to. the hand-wheel.

To this end the operating mechanism provided in accordance with the present invention involves the provision, on. the nut, of a coupling element which is carried by the nut so as always to be in engagement therewith but which is capable automatically of assuming one or the other of two operative or coupling positions in which, while still retained upon the nut, a portion of the coupling element protrudes from one side of the nut and engages either in a recess in the fixed part or in. recess in a rotar part constituted by the said hand-wheel. In one such position this coupling element, which is shown in the speci fic examples illustrated as consisting of a ball 42, of hardened steel for example, accommodated in a hole 42a which extends transversely through a radial flange portion Ilb of the nut, positively couples the nut with a fixed casing part constituted by a flange 44 of the steam chest I while in its other position the ball 42 positively couples the nut with the hand-wheel 31. To this end the said hole 42a. in the nut is open to both faces of the said flange [71b and they diameter of the ball exceeds the depth of the hole so that while the major portion of the ball remains in the hole a portion of the ball may protrude from one side of; the flange. and engages either in a recess 43 in the fixed casing part 44 or in a recess 45 in the hand-wheel. Also each recess is provided upon otherwise plain surfaces of their respective parts and with which plain surfaces the flange portion [lb of the nut has rotary engagement whereby in either coupled position of the ball, the latter is firmly held between the particular recess in which it has engaged and the opposite plain surface. the recess 43 is provided upon a plain surface 46 constituting the inner wall of the said flange 44 of the fixed casing and the recess 45 is provided in the plain annular and inner end surface 41 of the hub 38- ofi the hand-wheel.

The first such above-mentioned position is that which the ball normally occupies, i. e.when thevalve 3, i3 is closed and the steam ejector is in the fullyretracted position as shown in Figure 1 and with the coupling thus made the nut is restrained from rotating but the screwed spindle I6 is freetorotate through the nut. S'uch movement is purely axial and is possible due to the spline-like connections affordedby the parts 32', 33 on the one hand and the'parts 22, 23 on the other and the axial movement is sufficient fully to unseat the valve member: 1 3' and provide for a, full supply of steam tothe steam nozzle l I. At this moment it is desired that the steam ejector should be rotated and this takes place automatically when arr abutment pin 48 on the handwheel is brought up against andmade to cooperate with an abutment pin 48 on the nut; the two pins being disposed upon their respective parts to lie in the path of one'another and such that when the. valve I3 is fully seated they (the pins) are nearly diametrically opposite one another. The mechanism also involves the provision of a fixed pin 50 on the casing part l which protrudes into the path of a radial pin 5| on the outer periphery. of the nut I'l andwhich pin 5 (which, of course, is rotatable with the nut) in the normal or starting position of the parts lies against one side of'the fixed pin 50.

With the mechanism thus far described it is possible to refer to Figures. 3, 4 and 5 tounderstand the operation of the coupling...

Referring to: Figure 3, which represents the starting position of the parts, that is. when the steam ejectoris fully: retracted and the shut down valve 3:. i3 is fully seated", in this position the ball- 42 is in engagement with its retaining hole 42a in the nutll" and: protrudes also into the recess 43 in the flange of the fixed casing part i where it is hold fast by being locked between the recess 4?.- and the-- opposite plain surface 41 on the hub ofthe hand-wheel, so that the nut is now positively held against rotation and consequently" rotation of the steam ejector is also prevented. On rotation of the hand-whecl ina clockwise direction the recess 45 thereon will, after a half revolution, be brought opposite the ball 42; as seen in Figure 4 and at this point also the pin 49 onthe hand-wheelwillhave made half a rvelution' and will be brought'iip against the pin 48' on the nut. Also at the termination-of this half revolution'of the hand-wheel and parts just described the screwed spindle-l6 will (and permitted by its splined connection 32, 33 with thehand-wh'eel) havemade one half of a completeturn through the stationary nut which will, in'l'the case of the embodiment of the invention accordingto Figure 1, have produced a purely axialmovem'ent of the movable valve part l3 of an extent suliicient fully to open the valve. 7

In the intermediate position of the parts therefore, as seen in Figure 4, the valve will be fully open and the coupling between the nut and'the fixed; part will still be effective. In other words, the ball-42 will still be engaged in the recess 43 ur ne fixed part although the other recess 45 is now opposite it, but continued rotation of the hand-wheel in a clockwise direction will now cause'the pin 49on the hand-wheel to press against the pin lfion the nut and thereby con strain'the nut to rotate, the immediate eifect of whichwill be to cause the ball 42 to be shifted positively sideways or axially into engagement withtherecess 45in the hand-Wheel so that as, during continued rotation, the ball is moved 'a'wayirom the fixed recess 43 and the ball be.

comes locked between the other recess 45 and the'plain fixed surface 45, a positive coupling is made between the nut and the hand-wheel and this coupling cannot be broken until the mo tion' of the hand wheel has been reversed and the ball brjought'back again to lie opposite the recess 43 in the fixed casing part. "f Continued rotation of the hand-wheel in a clockwisedirection from the position of the parts, as seen in Figure 4 but with the coupling effective as, between the nut and the hand-wheel, will take place until the pin 5| on the outer periphery 'of thenut is brought up against the fixed pin 50 when further rotation of the handwh'eelinfa' clockwise direction is arrested and this after the hand-wheel has made somewhat less than one complete rotation, thereby ensuring that the recess 43' inthe fixed casing part 44 is not brought, opposite the ball (still coupled withthe hand-Rwheel) at this time. The positionof the parts, at this stage is shown in Figure 5 andcompared with, the position as shown in Figure l the effect of moving the parts from the one position to the other'will have caused the steam nozzle H, by therrotation of the nut and the engagement of its fingers 23 with the sides of the slot 22, tohave partaken of a purely rotary motion in" a 'clockwise direction which will be sufiicientf' to cause the steam nozzle, in its now pro'jectedposition, to traverse the required tube area but which rotary motion will be less than 360 due to the'engagement of the pin 5! on the outerperiphery of the nut with the fixed pin As stated, with the position of the parts as illustrated in Figure 5,]the engagement of the pin 5| on the nut withthe fixed pin 5o'prevents further rotational movementof the hand-Wheel in a clockwise direction and the parts therefore are nowr'eady to be returned to their original position" asshown in Figure 3 by rotation of the hand-wheel"in the opposite direction, that is, anti-clockwise, Itwill be observed that during the last part of the, clockwise rotation of the parts from the position shown in Figure 4 to that shown in'Figure 5, the clockwise rotation of the nut is imparted both by theengagement of the pins and 49 "as well asby the positive coupling -of the inutto the hand-wheel by the 'ball 42. :On reversing the direction of rotation, that is, by rotating the hand-wheel anti-clockwise, the pins 48 and 49 (which constitute a one-way drive) are no longer effective to'rotate the nut, but their relative positions continue to remain the .same due to the fact that the ball 42 still-functions to lock the nut positively to the hand-wheel and it is this positive lock which serves to cause the anti-clockwise rotation of the hand-wheel to be imparted to the nut, which continues until the pin 5! on the nut is brought up against the right hand side of the fixed pin 50 corresponding to the starting position, as shownin Figure 3. In this position the steam nozzle will have been rotated back to its zero or starting position and the ball (still engaged in the recess 45 in the hand-wheel) will be located opposite the recess 43 in the fixed casing part; That is to say the ball and two recesses will now all be in line with each other. The'nut is now held against further rotation anti-clockwise but the handwheel is still free-to turn anti-clockwise' 'and must have its motion in this direction continued as the steam nozzle, although in its zero position,

considered circurnierentially, is still in its axially projected position and the valve 3, i3 is therefore still. open and further rotation of'the'h'and-Wheel anti-clockwise is therefore necessary in order to retract the nozzle and seat (or fully close) the valve. Such further rotation of the hand-wheel anti-clockwise will however be accompanied by a lateral and positive shifting of the ball 42 from its coupling engagement with the recess 45 in the hand-wheel into its other coupling positionin which it protrudes into the fixed recess 43; The hand-wheel 3! is therefore again freed from rotation with the nut and during the last half revolution. anti-clockwise is able to rotate the screwed spindle relatively to the nut and cause the spindle to be retracted through the nut and draw along with it the piston is and the steam ejector and associated partsuntil the movable valve part I3 is seated firmly upon its seat 3; whenthis occurs further rotation of the hand-Wheel anticlockwise will be arrested and the parts will" be restored to their original positions as shown in Figure 3', the ball 42 being still in coupling engagement with the fixed recess 43 and'the recess 45 in the hand-Wheel being now diametrically opposite the ball The embodiment of the invention as illustrated in Figure 1 is suitable for use when merely a part (in this case one half) of a complete turn of the hand-wheel is sufiicient fully to open the valve 3, 13. If a longer axial movement of the steam ejector is required such that more than one complete rotation of the screwed spindle must take place before the required axial movement is obtained a modification of the invention is necessary and such a modification is illustrated in Figure 6 wherein the parts thereof corresponding to the same parts in Figure 1 are given the same reference numerals.

The essential difference between the construction of' the apparatus according to Figure 6 and that according to Figure 1 resides in the provision of the piston with an axial slot 52 which the fixed pin 50 normally (that is in the closed position of the valve) engages, and in forming the piston with a, reduced portion which provides an annular space 53 surrounding this portion of the piston and to which space'the axial slot 52 is openat one end Also the pins 48 and 49 on the nut and hand-wheelrespeo timely; as shown in Figure; I, are replaced. in. the modification according to Figure 61 bya pin 54 suitably located on. the screwed spindle. in con-. tacttwith. or in close proximity to the last turn of. the. thread on said spindle and a radial ShOlll'. den or. abutment 55 provided by removing. a shortlength ofthethread on the nut. I! atits lead-in, whereby the pin 54. will abut against the shoulder 55 at the appropriate moment dur: ing the. rotation of the screwed. spindle. That istosay, only when the screwed spindle has been advanced sufficiently to cause the pin54 thereon. to; be brought upagainst this abutment 55 on the nut will thev latter be constrained to rotate and the arrangement (which forms a one-way drive.) is such that at this; moment the fixed pin 50 (which was previously engaged in the axial slot 52 in the piston and prevented rotation ofthe piston and hence of the steam ejector) will be located opposite the annular groove 53 so; that rotation of the nut is permitted to take place due to the change over of the coupling position of the ball 42 which, as in the previous embodiment, will normally couple the nut I! to the fixed casing. Thus normally, that is when the. valve is closed and the steam ejector retracted the ball 42 will protrude into the recess 43 in. the fixed casing part 44 and although during each complete rotation of the handwheel 3.1 the other recess 45 will be brought opposite the ball, the latter will retain its coupling engagement with the; fixed recess 43; until the time arrives when not only will the recess 45 be opposite the ballbut the pin 54 will bebrought up against the abutment 55.

r The operation of the mechanism illustrated in Figure. 6 isas follows:

. Withthe valve [3 closed against its seat 3 and with the parts otherwise as illustrated in the figuregupon the hand-wheel 3'! being rotated clockwise, the screwed spindle will be rotated through the. nut (which is now held stationary by thev ball 42 coupling the nut to the fixed casing part 4.4) and produce a purely axial movement of the steam ejector. so long as the fixed pin. 50 remains in engagement with the axial slot. 52 in the piston and. the arrangement is such that, when. the. second last turn of the handwheel 31' is reached the fixed pin 55 leaves the axial. groove. 52 and enters the circular or annular groove 53 at the same time as the pin 54. on. the screwed spindle is brought. up. against the screw-thread end or abutment 55,1. Consequently continued rotation of. the hand-wwheel clockwise will cause the. ball; 42 to. be, shifted sideways in its hole 42a in the nut so that it now protrudes into. the. aligned recess 45 on the hand-wheel and accordingly the nut is now constrained to. rotate. with the hand-wheel. Continued rotationof the hand-wheel clockwise for another complete revolution will cause, a radial stop. 56 on the reduced piston portion to be brought up-against. the. fixed pin (this cor-1 responding to the position. of the. pin; 5| with. the pin. 5.0. as seenin Figure 5 and. further rotation of the. hand-wheel clockwise will then be arrested; Upon rotatingthe. hand-wheel. anti.- clockwise the pin. 54 on the screwedspindle ceases). to. function but the. ball remains locked in. position between. thehandwheel and the nut until. the. ball is brought opposite. to the. recess s. in the fixed casin par W this was further rotationofj the. hand-wheel anti-clock: wise will cause the ball to be..pu$1'1 .ed. sidewayg can i s h le mm he n t and.- into ex le gagement. with the recess 43, because. at that time: the fixed pin 50 will have again comeup against the radial stop 56 on the reduced piston portion where the fixed pin 50 will be aligned with the axial slot 52 in the piston. Continued rotation of the hand-wheel, therefore, clockwise will then cause the screwed spindle to be retracted through the nut and produce a purely axial retracting movement of the steam ejector by the engagement of the fixed pin 50 with the axial slot 52 until the movable valve member l-3 has been fully seated against its seat 3 when further, rotation of the hand-wheel anti-clockwise will be.- arrested.

In both modifications of the invention according to Figures 1 and 6 the ball 42 provides a definite mechanical lock between the nut and the operating handle (the rotary part) when once the ball has been engaged in the recess in the hand-wheel and such lock cannot be broken until the hand-wheel has been rotated backwards to bring these parts into their original position.

The recesses 43 and 45 are preferably made tohave a V-shape section as shown which facilitates their production by a simple boring operation and also provides for the obtaining of the required frictional engagement of the protruding ball portion with either recess but the recess is not necessarily limited to such shape.

The piston I5. is formed at its inner end with an. end face i5d which is presented to the steam admitted to the steam chest through the steam inlet i8, via a bore 6a in the steam branch 6; and it the area of the end face is greater than that of the. inner end surface of the shut-down valve. or of the ejector at the opposite end of the steam chest there will be a rearward loading of the piston by the steam, with respect to the direction of flow of the steam to the ejector, and asa consequence. the piston will tend to be maintained in close frictional engagement with the disc 28 at the inner end of the screwed spindle 1'6.

The steam branch 6 has the bore 5a through which the steam from the main steam supply pipe. flows to the steam chest and another bore 61). in which the forward end of the steam chest is. received and both bores terminate at a common. end surface IQ of the steam chest, whereby it is possible to effect a steam-tight joint with the. corresponding end surface 20.. of the steam chest by the single jointing member I, which is disposed in one and the same plane. The arrangement permits of the use of the fixed valve seat 3 in rear of the steam inlet I8, having regard to the direction of flow of the steam, while permitting. of the interior of the apparatus being withdrawn without the necessity of breakingthe steam joint between the end surface 2'! of the steam branch and the main steam supply pipe.

In either modification of the invention provision is made for the. escape of any steam which may pass to. the rear of. the piston and this withoutthe disadvantages of such steam upsetting the piston balance. To this end in Figure. 1. the steam chest, is provided. with av steam; vent 55 while in. Figure 5 the fixed pin 52. has a hollow bore 51; which acts as. a steam vent.

While it is. intended that the ball should be. shiftable. bodily within its hole in the nut so that a portion of the. ball may protrude from one or the, opposite face of the. nut it may be preferable. to provide slight reductions of the hole. at the. ends thereof, sufficient. to prevent the ball from falling out of the hole when the operating mechanism is dismantled, yet such as will not prevent the required shifting movement from taking place.

We claim:

1. Apparatus for cleaning boiler tubes in combination a casing, an ejector nozzle mounted in said casing for axial movement for projection therefrom, and for rotational movement about its axis for traversing fluid discharged from said nozzle, and means for projecting and rotating said nozzle consisting of a rotatably mounted screw-threaded actuating member connected to said nozzle by means which permits rotation relatively thereto and prevents relative axial movement of nozzle and actuating member, a nut engaging said actuating member, means connecting said nut and said nozzle which permits axial movement of said nozzle relative to said nut and prevents relative rotation of said nut and said nozzle, means normally locking said nut to said casing, means responsive to the relative rotary positions of said actuating member and said nut to release said nut from said casing and to lock said nut to said actuating member whereby initial rotation of said actuating member rotates said member relative to said nut to project said nozzle axially until said nut is released from said casing and is locked to said actuating member, whereupon continued rotation of said actuating member rotates said nut, and said nozzle driven thereby, and arrests further axial movement of said nozzle.

2. Apparatus as claimed in claim 1, wherein the locking means comprises a ball retained and moveable longitudinally in a transverse bore in the nut, that portion of the nut containing the ball being rotatable in engagement on one side face thereof with an interior surface of the casing, and a manually operable member with an end face with which the other side face of said nut is in rotatable engagement, said manually operable memberbeing mounted for rotation in the casing and having splined connection with said actuating member for operation thereof, and the casing and said manually operable memher having a recess into which a portion of said ball can protrude from said bore in the nut, respectively, for locking the nut to the casing and the nut to said actuating member.

3. Apparatus as claimed in claim 2, wherein the nut and the manually rotatable member are provided with abutments on the nut and the manually rotatable member, respectively, which come into contact with one another when the actuating member has been turned a predetermined amount in one direction by rotation of the manually rotatable member, and stop means is provided to arrest the rotary movement of the nut subsequent to further rotation of the manually rotatable member in said direction.

4. Apparatus as claimed in claim 3, wherein said stop means consists of a pin secured to the casing, and a piston secured to the ejector nozzle and having a composite slot or groove in which said pin engages, which composite slot comprises an axially extending portion and an annular portion, the latter having an abutment with which the pin contacts to arrest the nut during said further rotation of the manually rotatable member.

5. In combination, a fixed part, a rotatable part,

a rotatable threaded spindla'a driving connection between said rotatable part and said spindle, a nut threaded on said spindle, said nut being formed to provide a carrier portion, a locking element movable in said carrier portion to protrude into a recess in said fixed part to lock said nut from rotation with said spindle, and protrude in a second position into a recess in said rotatable part to release said nut and lock said nut to said spindle for rotation therewith, said fixed part and said rotatable part having crammed surfaces, respectively, which during rotation of said spindle force said locking element into said position to positively lock said nut to said fixed part in one position and to said rotatable part in said second position.

CHARLES FLETCHER LUMB.

FRANK GEORGE WILLIAM SPEARS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 534,180 Smart Feb. 12, 1895 2,156,436 Simpson May 2, 1939 2,248,947 Bowers July 15, 1941 2,269,802 Wilson Jan. 13, 1942 2,432,027 Lumb et al Dec. 2, 1947 FOREIGN PATENTS Number Country Date 535,478 Great Britain Apr. 10, 1941 

